we play the old game for the same reason we started in the first place because the major powers have the ability to demand concessions because of the power of their militaries and economies.

Russia is a player because it has a vast army and nuclear weapons

if Ukraine wants to not do as they are told by Russia they are more than welcome to fight them. America and the other powers involving themselves in that fight risks major war however also it has proved ruinously expensive to the actual populations of those countries.

Internal politics only matter if they are backed up by something

this theory wasn't blindsided by the end of the cold war. At the end of the cold war Russia was weak from crisis (incidentally largely because the Ukrainian local government so badly fucked up running a power plant and the early stages of a disaster that all the money in the soviet union was required to clean up the mess) anyway when Russia was weak and eating itself they couldn't enforce the rights they had because of their strength now they are strong again they can